1. Field of the Invention
The present invention relates to a magnetoresistance head for use in a playback head of a magnetic record/playback device and similar devices and a manufacturing method of the same.
2. Description of the Related Art
While the development of-high density magnetic recording has progressed in recent years, and high density HDD systems such as for instance 800 Mb/inch.sup.2 have become commercially practical, there are demands for even higher HDD recording density. A magnoresistance head (hereinafter MR head) in which an external magnetic field modifies the electric resistance of certain types of magnetic thin-film and magnetic multi-layered thin-film and the like, namely magnetoresistance (hereinafter MR), is regarded as a potential playback head for such high density recording systems.
FIG. 44 shows a configuration example of a general shield-type MR head as used conventionally. In the diagram, 1 is a substrate consisting of Al.sub.2 O.sub.3.multidot.TiC and the like. A lower side shield layer 3 consisting of soft magnetic film such as permalloy is disposed an the substrate 1 with an insulating lower layer 2 consisting of Al.sub.2 O.sub.3 and the like in between. An MR film 5 is provided above the lower side shield layer 3 with a non-magnetic film 4 in between forming a playback magnetic gap, A pair of leads 6 are connected to both ends of the MR film 5 to form an MR element 7. An upper side shield layer 9 is disposed above the MR element via a non-magnetic film 8 forming a playback magnetic gap. The shield type MR head detects a signal magnetic field by passing a sensing current through the pair of leads 6 and measuring changes in the resistance accompanying changes in the average direction of magnetization.
However, the tracking width of a shield MR head of the type described above is defined by the width of the two leads 6. Consequently, in order to respond to an additional increase in recording density, the distance between the two leads 6 must be reduced, thereby further diminishing the region sensitive to the magnetization. The recording density of a shield MR head can therefore be increased only by a limited degree. Moreover, during the manufacturing of the leads 6, the conductive film which forms the leads 6 must be patterned in the shape of the leads. There is a great danger here in that part of the MR film 5 will suffer etching, resulting in a reduction in the properties of the MR film 5 or a reduction in the manufacturing yield.
Furthermore, since the MR film 5 makes direct contact with the polish and the like during depth setting, there has been the serious problem of MR film 5 corrosion during this process. Measures have been adopted to solve this problem, such as the provision of insulating protective film on the surfaces and the like of the MR head facing the medium. However, this method is not suitable for low magnetic head levitation which is indispensable for improving line recording density. Moreover, contact recording systems which are expected to become the prominent high density technology of the future have the disadvantage that the protective film may be destroyed due to abrasions on the surface facing the medium. When such abrasion reaches the MR film 5, the resulting fluctuations in depth direction width not only cause the output of the head to fluctuate, but lead to the additional danger that the MR film 5 itself may be destroyed due to abrasion. There is therefore a demand for measures to prevent abrasion on the MR film 5.
FIG. 45 shows an MR head known as a yoke type MR head which is conventionally used in order to avoid the problems of the shield MR head as described above, in which a magnetic yoke 10 lead a signal magnetic field to an MR element 7 disposed within the head. In this yoke type MR head, an MR element 7 is disposed on a soft magnetic layer 11 which forms part of the magnetic yoke 10 with a non-magnetic film 12 forming a magnetic gap provided in between. Furthermore, MR film 5 is arranged between soft magnetic materials 13 and 14 forming one portion of the magnetic yoke 10 which are provided respectively from the surface facing the medium so as to connect with the soft magnetic layer 11 inside the head.
In the conventional yoke type MR head described above, the leads 6 are disposed in exactly the same way as in the shield MR head. Therefore, head properties and yield are liable to deteriorate due to etching reaching the MR film 5. Furthermore, playback output is liable to fluctuate depending on the state of the connection between the position of the MR element 7 and the magnetic yoke 10, or as a result of alignment differences and such like between the MR film 5 and the soft magnetic materials 13 and 14 forming part of the magnetic yoke 10. It has consequently been difficult to manufacture MR heads having all the desirable properties with a high yield.
Alternatively, a configuration has been suggested in which a magnetic core 15 is provided on the substrate 1 in the lamination direction and an MR element 7 is disposed inside the magnetic care 15 as depicted in FIG. 46.
As before, however, the playback output of this configuration is low, since the magnetic permeability rate is the thickness direction of the film of the magnetic core 15 is virtually zero and the MR element 7 is moved back from the surface facing the medium only as far as the thickness of the film of the magnetic core 15. Furthermore, it is difficult to reduce costs when using a conventional yoke type MR head as described above since the manufacturing processes of both the magnetic yoke and the leads are complex.
Conventional yoke type MR heads have had the additional disadvantage that Barkhausen jumps in the magnetic yoke are liable to generate noise. In other words, in a case in which the direction of the magnetic path formed by the signal magnetic field is parallel to the axis of easy magnetization of the magnetic yoke, an abrupt magnetic reversal occurs when the signal magnetic field is reversed, thereby causing signal noise such as Barkhausen noise.
Positioning the axis of easy magnetization of the magnetic yoke at a right angle to the direction of the magnetic path is one accepted method of reducing such signal noise. When using a magnetic yoke having an indented portion such as the magnetic yoke 15 shown in FIG. 46 for instance, the aim is to induce magnetic anisotropy at a right angle to the direction of the magnetic path to every part of the indented portion of the magnetic yoke.
Formation of the film within a magnetic field and annealing (heat processing) in a Magnetic field are conventional methods of inducing magnetic anisotropy. An ordinary external coil is used as a means of applying the magnetic field in such magnetic field film formation and annealing in the magnetic field. However, since an external coil can only apply a magnetic field in one direction, it is not possible to apply an axis of easy magnetization at a right angle to the magnetic path direction to the whole of a magnetic yoke having an indented portion.
As explained above, when the distance between leads required for high density recording is reduced in a conventional shield MR head, the region sensitive to magnetic fields is lessened. This limits high density recording capability. A conventional MR head has the additional disadvantages that etching may reach the MR film during the manufacturing process of the leads, the MR film is liable to corrode, and abrasions on the MR film can lead not only to fluctuating head output but also destruction of the MR film itself.
Alternatively, a yoke type MR head is regarded as potentially capable of use in high density recording since a yoke type MR head avoids problems related to abrasion on MR elements when implementing low magnetic levitation record/playback or contact system record/playback. However, like the shield MR head, the conventional yoke type MR head has the drawback that head properties and yield are liable to deteriorate as a result of etching reaching the MR film during the leads are arranged. In addition, the complex manufacturing processes of the magnetic yoke and the leads and the like make it difficult to reduce costs.
Furthermore, a conventional yoke type MR head has the disadvantage that Barkhausen noise is liable to be generated when magnetic domains are created or a magnetization direction is reversed in the magnetic yoke. Barkhausen noise can be reduced by for instance controlling the magnetic anisotropy of the magnetic yoke. However, in conventional methods of inducing magnetic anisotropy, it has been extremely awkward to control the axis of easy magnetization of an entire magnetic yoke having an indented portion in order that the direction of the axis of easy magnetization is at a right angle to the magnetic path. In addition, a conventional yoke type MR head has the disadvantage that playback output is low and variable output is liable to occur.